Fastest Bus Powered USB3 external HD?

I'm looking for the fastest bus powered USB 3.0 external HD for use with my macbook pro. I would LOVE at least 2TB, but can get by with less if necessary. I'm looking to stream samples for music composition, so it needs to access thousands of small files from different part of the disk as quickly as possible.

I was thinking of getting the Western Digital My Passport 2 TB USB 3.0 (goes for $180 at Amazon), which says it has a 5 Gb/s (Max), but it doesn't say how fast the actual drive is. Are there any drives by different manufacturers as big and fast (or faster) for less? For example, I found a Seagate GoFlex 1.5TB portable HD at Costco for only $99, but seagate says NOTHING about the specs/speed!

I'm currently using a Seagate 3TB GoFlex Desk USB 3 External Drive, which is working very well, but I dont like having the power brick. Or will switching from a 3.5" to a 2.5" sacrifice performance, no matter which brand I go with, due to the slower throughput on 2.5 drives?

It looks like you need to get an enclosure and a 7200 RPM bare drive and assemble it, since the budget external hard disks like the one you found at Costco are most likely 5400 RPM (price is the selling point - not performance) That said, it will probably be hard to get a significant, if any, performance increase over USB 3.0 interfaced desktop drives. Since you are accessing a bunch of small files a SSD would be a solid upgrade since the IOPS performance is superior, but you could only get a 256GB drive in the price range you mentioned.

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